Considerations for an Anaerobic Digester for your farm

Do I want to reduce manure odor coming from my farm?

Yes. An anaerobic digester is an excellent addition to a manure management system for the reduction in near odorless effluent for spreading on fields. The odor issue is becoming more and more of a problem as new residential housing developments are built closer and closer to the family farms of America. These new home owners find the smell of manure spread on fields offensive.

What type of digester do I need?

It depends on what type of manure management you are currently using, whether it is a scraped, flushed or belt system. The amount of water added to the manure from milking parlors and flush systems will have an impact on which digester is best suited for your farm. The reason this is important is because it affects the total volatile solids in the influent entering the digester. Also, the area of the country you live in plays a major role in the decision of which type of digester is to be used. In warmer areas of the country a covered lagoon is an option, because this type of digester uses ambient temperature to digest the manure. Lagoons are typically built at a lower cost. In the colder climates of the country, Complete Mix, Plug Flow or Temperature Phase (TPAD) digesters are preferred, because these types are easily heated.

Do I want to generate electricity to power the farm?

Possibly. Depending on the type and size of your animal operation and the way you are currently handing your manure, if this will be a viable option. Some reports have shown that at least 300 cows would be needed to produce enough biogas to generate electricity to meet all the power needs to run the farm. The additional cost involved in adding an engine generator set need to be considered.

Do I want to sell excess electricity to the power grid?

This can be an expensive add-on to your manure management system. Depending on how many animals you have, how much biogas can be produced to run an engine generator set to supply enough electricity to sell to your local power company. The biggest obstacle in the past has been to get a good price for the power you sell to the power grid. Power companies are not always willing to pay you enough per kW hour to off-set the cost of the engine generator set over a reasonable amount of time. Some U.S. states are starting to realize the potential of on-farm electric generation. Each individual state has their own financial assistance loan and/or grant programs for the construction of digester facilities.